Please read both narrations in Bukhari
It is very clear in arabic narration, they tried to twist the translation but still you can find it that Umar bin Khattab was between those people who run away. Only few companions remained with the holy Prophet, everybody else run away. Quran also states the situation about Hunain (9:25).
We find the Umar bin Khattab’s words that this is Allah’s order or Allah’s will to run away. We want to share Allah’s order from Quran that it is very sever to run away in battle field especially leaving the holy prophet in the hands of enemies and saving own life.
Please read the verse of Quran (8;15-16)”O you who believe! when you meet those who disbelieve marching for war, then turn not your backs to them.And whoever shall turn his back to them on that day– unless he turn aside for the sake of fighting or withdraws to a company– then he, indeed, becomes deserving of Allah’s wrath, and his abode is hell; and an evil destination shall it be.
We should not have difficulty to understand this reality that anybody who run away in the battle by leaving the holy Prophet in the hands of enimies, it clearly means it that the faith is not deeply penetarted to his heart. We also know that the war of Hunain was fought at the end times of holy prophet, after the victory of Mecca. It is not the earliar time of Islam, as our Sunni fellows say that the companions run away in OHad only 12 people remained. It was earliar time, they did not learnt much about Islam from the Prophet. But the battle of Hunain is the end time.